Anti-siphon features for control valves have previously been available. A typical drawback to many of these valves is that, upon opening of the valve, an instantaneous spray of fluid out of the air vent openings occurs. When such valves are used outside of buildings, the small amount of instantaneous spray is generally not important. However, for household use, such outward spray could not be tolerated.
Poppet-type anti-siphon valves have typically been part of a flow-control device employing a stem valve. Where it is desired to employ all of the fluid pressure available, a stem valve is disadvantageous because it provides an impediment to full flow and causes a pressure drop in the fluid.